Conventionally, a vehicle lamp using a light emitting element such as, for example, a light emitting diode (LED) as a light source has been suggested. The light emitting element tends to generate heat in accordance with a light emission thereby increasing a temperature, and further, the light emission efficiency of the light emitting element is affected by the temperature. Thus, in the conventional vehicle lamp, the temperature increase is suppressed by transferring the heat from the light emitting element to a heat dissipating member in order to keep the temperature of the light emitting element within a range suitable for the light emission.
For example, the conventional technology disclosed in Japanese Patent Laid-Open Publication No. 2012-064493 relates to a vehicle lamp in which a light emitting diode is mounted on a circuit board and faces a reflector so as to irradiate light to the front side of a vehicle. In addition, an aluminum-made light source support member is used as a heat sink to dissipate the heat generated from the light emitting diode. The heat sink is in contact with the rear surface of the circuit board so as to dissipate the heat from the light emitting diode to the outside through the circuit board and the heat sink.
In the conventional technology, a heat conducting member having excellent heat conductivity is generally interposed between the heat sink and the circuit board in order to effectively implement the heat conduction among the respective members. Further, since a wiring layer may also be formed on the rear side of the circuit board, it is also demanded to secure an insulation between the heat sink and the circuit board which are made of a metal.
As the heat conducting member meeting both the excellent heat conductivity and the insulation, a heat conducting sheet pre-molded in a sheet form may be used. However, since a process of bonding the heat conducting sheet is required, the number of assembly processes increases thereby deteriorating the workability, and since the heat conducting sheet is relatively expensive, the manufacturing costs increase. In addition, when the heat conducting sheet is used, a predetermined pressure is applied in a state where the heat conducting sheet is inserted between the heat sink and the circuit board, so as to compress the heat conducting sheet, and the heat sink and the circuit board are held in the state where the heat conducting sheet is compressed. In this case, there are problems in that, since a resin board used as the circuit board is compressed by the heat conducting sheet from the rear surface side, a warpage of the board occurs thereby causing the position of the light emitting element to be deviated from a focal point of the reflector, and as a result, an adjustment for obtaining a desired light irradiation range becomes complicated.